The goal of this Mentored Patient-Oriented Research Career Development Award (K23) is to prepare Dr. Bagner for an independent clinical research career focused on developing preventive interventions for infants and their families. Dr. Bagner's long-term career goals are to develop a transdiciplinary research program examining effective interventions for infants at risk for externalizing behavior problems and help advance evidence-based practice for infants with other behavioral and emotional problems. In the context of the K23 training plan, Dr. Bagner's short-term training goals are to: (1) acquire specialized training in the unique processes of infant development, including typical and at-risk populations, and the nature of relationship-based interventions; (2) gain knowledge and expertise in the design, execution, and analysis of conducting home- based prevention trials with infants and their families; and (3) broaden understanding of ethical and multicultural issues relevant to conducting intervention research with low-income families. This training plan will be facilitated by: (a) expert mentorship from Drs. Wendy Silverman, Barry Lester, David Olds, Lorraine Bahrick, Alice Carter, James Jaccard, William Pelham, and Jose Rosa-Olivares; (b) formal coursework and seminars; (c) directed readings; (d) focused clinical experiences in the area of infant mental health; (e) the diverse resources available at Florida International University and Miami Children's Hospital; and (f) implementation of the proposed research project. Dr. Bagner will implement a 5-year research study in which he will develop and evaluate the potential efficacy of a preventive intervention for infants at risk for externalizing behavior problems. The intervention will be an adaptation of Parent-Child Interaction Therapy for use with infants in the home setting (i.e., PCIT-I). The first 18 months of the proposed award will be devoted to developing PCIT-I and piloting it in an open trial. Subsequently, Dr. Bagner will conduct a small randomized trial comparing PCIT-I to standard care. Data concerning the feasibility and acceptability of PCIT-I and clinical significance of findings, combined with results from statistical analyses, will be used to inform an R01 application for a stage II clinical trial. PUBLIC HEALTH RELEVANCE: Negative outcomes of early externalizing behavior problems in childhood are overrepresented in low-income families and represent a significant public health concern. Despite recent findings that externalizing behavior problems can be identified as early as 12 months, there has been limited research examining the prevention of later externalizing behavior problems in infants from low-income families.